A number of different windscreen covers have been tried over time, but none works satisfactorily, and wind noise is still a major disturbance for people who wear hearing aids. Mesh screens have been used, but even if they may dampen wind-noise they have a strong tendency to clog as dirt is inevitably caught and squeezed into the mesh. Also, mesh screens will not keep water out of the microphone opening. Phonak AG has developed a windscreen disclosed in EP 0847227 made of sintered polymer, foamed ceramic, sintered glass or sintered metal. The developed cover is hydrophobic and-or oleo phobic. This prior art cover is with small open pores, whereto a “Teflon” (RTM) applied. This cover suffers from the problem that it is not fully sound transparent and also it is rather expensive. None of the prior art techniques seem to provide a microphone cover which both protects the microphone against pollution from the surroundings and diminishes the problems relating to wind-noise in a satisfactory way, while at the same time allows free passage for sound from the surroundings to the microphone element.